I'm not quite sure were your aiming at here but here goes
Anyways. when you refresh or recompose a machine a user first needs to be logged off, after that the machine can be recomposed, that's how View works.
If, for some reason, an appstack or writable volume is still attached to a machine, if you recompose or refresh the appstacks and writable volumes will be detached after the machine has been reconfigure.
If you remove the machine after use and the appstack and writable volume is still attached, writable volume will be deleted (because it is read/write) and appstack will simply be detached because it is read-only.